Tropical Cyclone Narelle has been upgraded to a category four as it continues to move closer to the Pilbara coast.

The Bureau of Meteorology says a cyclone warning remains in place for coastal areas from Whim Creek to Coral Bay, including Karratha, Dampier, Onslow and Exmouth.

At 2am, Narelle was estimated to be 570km north of Exmouth and 515km north northwest of Karratha and moving southwest at 16km/h.

Gales with gusts to 100km/h are expected to develop in coastal areas between Whim Creek and Exmouth during Friday afternoon, then extend south to Coral Bay on Saturday morning.

Residents on the Pilbara coast are being warned to prepare for possibly destructive wind gusts over 130km/h overnight on Saturday.

Thunderstorm activity is also expected to increase about the Pilbara coast on Friday with isolated heavy rainfall and squalls possible.

WA's multibillion-dollar resources industry has already reacted, with iron ore ports at Cape Lambert and Dampier due to close, and Apache closing down the Stag and Van Gogh oil fields on Thursday.

Chevron is also getting ready to evacuate workers from Barrow Island.

WorkSafe WA Commissioner Lex McCulloch warned companies on land and sea that it was crucial to be prepared.

"The worst thing people can do is underestimate the power of a cyclone. Seven people died as a result of Cyclone Bobby in February 1995, and three more lives were lost during Cyclone George in March 2007," Mr McCulloch said.

Airlines, including Cobham and Qantas, are scheduling flights to evacuate workers from North West drilling platforms and mining sites.